Arthropods

In
this LOARS Web Resource we are only
concerned with the Arthropods which are found between the tides on rocky
ocean shores.

One
of the major classes within the Crustacean group is the Malacostracans.
This group contains the lobsters, crabs and prawns. See the diagram above
for the Malacostracan body parts.

Arthropods
are a massive group of animals and have many more varieties, or species,
than all the other groups combined. It is believed that 75% of all animals
are Arthropods.

The
name arthropod is made up from "arthro" meaning joint,
and "pod" meaning leg. Arthropod legs are highly adapted
for walking, swimming, feeding and gathering sensory information.

Some arthropods,
such as decapod crabs can regrow severed
limbs in a process called "regeneration".

Arthropods
have a number of characteristics which are common.

A
hardened external skeleton (exoskeleton) made of a protein called
chiton, which covers and protects the body.

This hardened shell gives rigid support for the attachment
of an arthropod's internal muscles.

The
exoskeleton consists of several separated plates connected by thin
membranes, which form joints. These flexible membranes allow the
arthropod to flex its otherwise hardened body, legs, mouthparts and
antennae to allow movement.

Periodically, every
arthropod becomes too large for its outer shell and must shed its
exoskeleton, in a process called moulting. Moulting is
a particularly trying time for arthropods and they can become very
vulnerable to predators at this time

Most arthropods have eyes.

Most arthropods have
two separate sexes. However, some arthropods, such as the barnacles,
are hermaphroditic. This means that one individual is both
sexes at the same time.